JP2556956Y2 - Shroud opening structure for cooling air intake of air-cooled internal combustion engine - Google Patents

Description

[Detailed description of the invention]

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a shroud opening structure for taking in cooling air of an air-cooled internal combustion engine having a low ventilation resistance and excellent sound insulation.

[0002]

2. Description of the Related Art A heat radiating portion of an internal combustion engine is covered with a shroud, and cooling air is introduced into a shroud through a cooling air intake opening formed in the shroud by rotation of a cooling fan integral with a crankshaft. In an air-cooled scooter-type motorcycle air-cooled internal combustion engine, as shown in Japanese Utility Model Publication No. 63-32903, from the inside to the outside, as shown in Japanese Patent Publication No. 63-32903 in order to achieve sound insulation and to prevent external rainwater from being introduced into the shroud. A louver is provided at the cooling air intake opening of the shroud, in which thin plates inclined downward from above are arranged in parallel at required intervals in the vertical direction.

[0003]

In the shroud described in the above publication, in order to improve the directivity of noise and improve the sound insulation,
Outside the inner louver integrated with the shroud, a separate outer louver having a thin plate arranged on an extension surface of the thin plate of the inner louver is detachably mounted to expand the width of the thin plate, as shown in FIG. As described above, the cross-sectional area of the air passages of the spaces 03a and 03b surrounded by the open cylindrical wall 01 and the inclined direction end side thin plates 02a and 02b increases and decreases from the upstream side to the downstream side, and the air resistance increases. And the cooling performance deteriorated.

[0004]

SUMMARY OF THE INVENTION The present invention relates to an improvement in a shroud opening structure for taking in cooling air of an air-cooled internal combustion engine which solves such a problem, and covers a heat radiating portion of the internal combustion engine with a shroud. An air-cooled internal combustion engine that cools the radiator by introducing cooling air into the shroud by rotating a cooling fan from a cooling air intake opening formed in the shroud, wherein the cooling air intake opening inner peripheral wall includes: A louver in which the thin plate is oriented in a parallel direction, passes through the center of the opening, and is bent around a center line parallel to the inner peripheral wall of the opening, and the thin plate is formed in multiple layers in a radial direction from the center of the opening. The cooling air intake opening is provided.

In the present invention, as described above, the louver is formed by bending the thin plate around the line passing through the center of the cooling air intake opening and forming the louver in multiple layers from the center of the opening in the radial direction. Since the cooling air passing between the thin plates can be discharged to the outside without diffusing not only in the vertical direction but also in the horizontal direction, the directivity of noise can be enhanced and the sound insulation effect can be improved.

Further, in the present invention, since the curved thin plate is directed parallel to the inner peripheral wall of the cooling air intake opening, the cross-sectional area of the cooling air passage between the curved thin plates does not change in the cooling air traveling direction. In addition to being constant, the cross-sectional area of the cooling air passage between the inner peripheral wall of the opening and the curved thin plate is also constant, so that the cooling air passage resistance is reduced and the cooling effect is maintained at a high level.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention shown in FIGS. 1 to 3 will be described below. The swing-type power unit 2 mounted on the scooter-type motorcycle 1 includes an air-cooled internal combustion engine 3 in which the air-cooled internal combustion engine 3 stands up with the air-cooled internal combustion engine 3 inclined slightly backward and rearward, and a rearward portion from one lower side thereof. The extended V-belt type continuously variable transmission 4 is integrally connected to each other, and a rear wheel 5 is integrally fitted to an output shaft (not shown) of the V-belt type continuously variable transmission 4. The hanger 6 located at the front of the power unit 2 is attached to a bracket 8 projecting rearward from a vehicle body 7 of the scooter type motorcycle 1 so as to be swingable up and down.

The crankcase 9 of the air-cooled internal combustion engine 3
A variable drive pulley 11 of the V-belt type continuously variable transmission 4 is provided at the left end of the crankshaft 10 rotatably supported by the motor, and a driven variable pulley (not shown) pivotally supported at the rear of the transmission case 12. And a variable drive pulley 11, a V-belt 13 is stretched over, and as the rotational speed of the crankshaft 10 increases,
The speed ratio of the V-belt type continuously variable transmission 4 decreases steplessly,
The power of the air-cooled internal combustion engine 3 is transmitted to the rear wheels 5 via a V-belt type continuously variable transmission 4.

Further, the cylinder above the crankcase 9
14 and the cylinder head 15 above it,
The rotor 18 of the generator 17 is integrally fitted to the right end of the crankshaft 10, and a centrifugal cooling fan 19 is integrally attached to the rotor 18.

Furthermore, a shroud 20 made of synthetic resin that covers the air-cooled internal combustion engine 3 and the cooling fan 19 is a cylinder-side shroud 21 that covers the cooling fan 19 and the cylinder 14 of the air-cooled internal combustion engine 3 and a head that covers the cylinder head 15. The shroud 22 includes a side shroud 22 and a shroud outer plate 23 that covers the outside of the cylinder side shroud 21. The cylinder side shroud 21 and the head side shroud 22 are detachably mounted to the crankcase 9, the cylinder 14, and the like with mounting bolts 24. It has become.

The cylindrical shroud 21 has a cylindrical opening wall 25 which is concentric with the cooling fan 19 and whose inner peripheral surface is parallel to the center line of the cooling fan 19, and a louver is formed on the cylindrical opening wall 25. 26, the louver 26 has a diameter that changes in an arithmetic progression about a center line passing through the center of the cylindrical opening wall 25 and directed in a direction perpendicular to the opening surface of the cylindrical opening wall 25. It comprises a cylindrical thin plate 27, and a connecting plate 28 arranged in a cross so as to connect the cylindrical opening wall 25 and the cylindrical thin plate 27 to each other and to connect the adjacent cylindrical thin plates 27 to each other. .

The cylinder-side shroud 21 is formed with a mounting seat 29 projecting outward at one location at the upper part and at two locations at the lower part. The shroud outer plate 23 is also provided at a location corresponding to the mounting seat 29. The mounting seat 30 protruding inward is formed,
A sound absorbing material 31 such as polyurethane sponge is interposed between the cylinder side shroud 21 and the shroud outer plate 23 over the entire side surface except the cylindrical opening wall 25, and rivets 32 are fitted to the mounting seats 29 and 30, and the cylinder side shroud 21, shroud skin 23
The cooling air sucked into the shroud 20 from the cylindrical opening wall 25 by the rotation of the cooling fan 19 passes through the cooling air passage 33 in the shroud 20 while the heat radiating thin plate 16 is After flowing to the cylinder head 15 side while touching, the cooling exhaust port on the left rear side of the head side shroud 22
It is released to the atmosphere from 34.

The illustrated embodiment is constructed as described above, so that the air-cooled internal combustion engine 3 starts to move and the cooling fan
When the rotary motor 19 is driven, the outside air on the right side of the swing type power unit 2 is introduced into the cooling air passage 33 in the shroud 20 from the cylindrical opening wall 25 and touches the heat radiation thin plate 16 of the cylinder 14 and the cylinder head 15. While the heat is being exchanged, the air is discharged from the cooling air outlet 34 to the outside of the shroud 20, and the cylinder 14 and the cylinder head 15 are sufficiently cooled.

Even if noise is generated from the air-cooled internal combustion engine 3 and the cooling fan 19 during the operation of the air-cooled internal combustion engine 3, the noise in the cooling air passage 33 is reduced by the shroud 20 that covers the air-cooled internal combustion engine 3 and the cooling fan 19. As a result, sound is absorbed by the sound absorbing material 31 between the cylinder-side shroud 21 and the shroud outer plate 23, and the noise level outside the swing type power unit 2 is significantly reduced.

Further, since the cylindrical thin plates 27 are provided concentrically in multiple layers in the cylindrical opening wall 25, noise passing through the cylindrical opening wall 25 is transmitted to the center line of the cylindrical opening wall 25. It is emitted with high directivity along, does not diffuse in all directions, and the noise level outside the shroud 20 further decreases.

Further, a cylindrical opening wall 25 and a cylindrical thin plate 27 are provided.
The cross-sectional area of the cooling air passage is constant from the inlet to the outlet, and the cross-sectional area of the cooling air passage in the plurality of cylindrical thin plates 27 is also constant from the inlet to the outlet. The resistance of the cooling air passage passing between the opening walls 25 is maintained at a low level, and a good cooling effect can be expected. Moreover, between the cylindrical opening wall 25 and the cylindrical thin plate 27 and between the plurality of cylindrical thin plates 27
By reducing the gap between them, the directivity of exhaust noise can be further improved.

In the embodiment shown in FIGS. 1 to 3, the center line of the cylindrical opening wall 25 coincides with the center line of the cooling fan 19, but as shown in FIG. The curved cross section forms a circular curved opening wall 35, and the outer end of the curved opening wall 35 has a louver 26 similar to the embodiment of FIGS.
In such an embodiment, since the noise emitted from the curved opening wall 35 is directed downward, the ear of the driver or the pedestrian on the road, which is riding on the scooter-type motorcycle 1, may be provided. And the noise level is further reduced.

The center line of the notched cylindrical opening wall (not shown) is directed obliquely downward with respect to the center line of the cooling fan 19 and is formed so as to be along a vertical plane perpendicular to the center line of the cooling fan 19. A slant-cut cylindrical opening wall is formed in a shape obtained by cutting the inner and outer opening edges of the opening wall, a slant-cut cylindrical thin plate of the louver is formed in the same manner, and a plurality of slant-cut cylindrical thin plates may be connected by a connecting plate. In this embodiment, the noise can be directed obliquely downward without extending the passage length of the opening wall.

In the embodiment shown in FIGS. 1 to 3, a plurality of cylindrical thin plates 27 are arranged concentrically.
As shown in FIG. 2, a spiral thin plate 36 may be used. In such an embodiment, one strip-shaped plate may be formed in a spiral shape, and a connecting plate 37 for connecting the spiral thin plates 36 to each other. The number of sheets can be reduced, reducing material and processing man-hours.
Cost can be reduced.

[Brief description of the drawings]

FIG. 1 is a rear right side view of a scooter type motorcycle provided with a shroud opening structure for cooling air intake of an air-cooled internal combustion engine according to the present invention.

FIG. 2 is a longitudinal sectional view taken along the line II-II of FIG.

FIG. 3 is an enlarged side view of a main part of FIG. 1;

FIG. 4 is an enlarged longitudinal sectional view of a main part of another embodiment of the present invention.

FIG. 5 is an enlarged side view of a main part of still another embodiment of the present invention.

FIG. 6 is a perspective view of an essential part of a shroud opening structure for taking in cooling air of a conventional air-cooled internal combustion engine.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Scooter type motorcycle, 2 ... Swing type power unit, 3 ... Air-cooled internal combustion engine, 4 ... V-belt type continuously variable transmission, 5 ... Rear wheel, 6 ... Hanger part, 7 ... Body, 8 ... Bracket, 9 ... Crank Case, 10 ... crankshaft, 11 ... variable drive pulley, 12 ... variable machine case, 13 ... V belt, 14 ...
Cylinder, 15: Cylinder head, 16: Heat dissipation thin plate, 17: Generator, 18: Rotor, 19: Centrifugal cooling fan, 20: Shroud, 21: Cylinder shroud, 22: Head shroud, 23: Shroud outer plate, 24 mounting bolts, 25 cylindrical opening wall, 26 louver, 27 cylindrical thin plate, 28 connecting plate, 29, 30 mounting seat, 31 sound absorbing material, 32 rivet, 33
Cooling air passage, 34 ... cooling air outlet, 35 ... curved opening wall, 36 ...
Spiral thin plate, 37 ... combined plate.

Claims (1)

(57) [Scope of request for utility model registration] 1. A heat radiating portion of an internal combustion engine is covered with a shroud,
In an air-cooled internal combustion engine that cools the radiator by introducing cooling air into the shroud by rotating a cooling fan through a cooling air intake opening formed in the shroud, the cooling air intake opening is parallel to an inner peripheral wall of the opening. The louver is formed by forming the thin plate in a direction in which the thin plate is oriented and passing through the center of the opening, and bending the thin plate around a center line parallel to the inner peripheral wall of the opening, and forming the thin plate in multiple layers from the center of the opening in the radial direction. A shroud opening structure for cooling air intake of an air-cooled internal combustion engine, wherein the shroud opening structure is provided at a cooling air intake opening.